/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hive.ql.parse;

import java.util.Collection;
import java.util.List;

import org.apache.hadoop.hive.ql.exec.TableScanOperator;
import org.apache.hadoop.hive.ql.metadata.Table;

public class ColumnAccessAnalyzer {
    private final ParseContext pGraphContext;

    public ColumnAccessAnalyzer() {
        pGraphContext = null;
    }

    public ColumnAccessAnalyzer(ParseContext pactx) {
        pGraphContext = pactx;
    }

    /*************************************************
     * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
     *  注释： 列访问分析 = 列裁剪
     */
    public ColumnAccessInfo analyzeColumnAccess(ColumnAccessInfo columnAccessInfo) throws SemanticException {
        if (columnAccessInfo == null) {
            columnAccessInfo = new ColumnAccessInfo();
        }
        Collection<TableScanOperator> topOps = pGraphContext.getTopOps().values();
        for (TableScanOperator top : topOps) {
            // if a table is inside view, we do not care about its authorization.
            if (!top.isInsideView()) {
                Table table = top.getConf().getTableMetadata();
                String tableName = table.getCompleteName();
                List<String> referenced = top.getReferencedColumns();
                for (String column : referenced) {
                    columnAccessInfo.add(tableName, column);
                }
                if (table.isPartitioned()) {
                    PrunedPartitionList parts = pGraphContext.getPrunedPartitions(table.getTableName(), top);
                    if (parts.getReferredPartCols() != null) {
                        for (String partKey : parts.getReferredPartCols()) {
                            columnAccessInfo.add(tableName, partKey);
                        }
                    }
                }
            }
        }
        return columnAccessInfo;
    }
}
